Develop Reference

Legend not appearing when using document.createElement('canvas')

I followed this Observable post to easily create a legend.
Since the line
DOM.canvas(1, n)
in the ramp works only on Observable, I replaced it with
document.createElement("canvas")
and also modified the SVG so that it's appended to the main div tag. These changed do not cause any errors however the problem is that the legend is not displayed even though the legend SVG is present in the raw HTML.
Here's the link to a JSFiddle. Any guidance would be greatly appreciated.

The canvas is being created, that's not the problem. The problem is that, since you are now missing the width and height in...
const canvas = DOM.canvas(n, 1);
//these are w & h --------^--^
... you now need to set those yourself. For instance:
d3.select(canvas).attr("width", n)
.attr("height", 1);
Here is a simplified version of that JSFiddle, showing that the canvas works:
legend({
color: d3.scaleSequential([1, 10], d3.interpolateReds),
title: "Title"
})
function legend({
color,
title,
tickSize = 6,
width = 320,
height = 44 + tickSize,
marginTop = 18,
marginRight = 0,
marginBottom = 16 + tickSize,
marginLeft = 0,
ticks = width / 64,
tickFormat,
tickValues
} = {}) {
const svg = d3.select(".scatter").append("svg")
.attr("width", width)
.attr("height", height)
.attr("viewBox", [0, 0, width, height])
.style("overflow", "visible")
.style("display", "block");
svg.append("image")
.attr("x", marginLeft)
.attr("y", marginTop)
.attr("width", width - marginLeft - marginRight)
.attr("height", height - marginTop - marginBottom)
.attr("preserveAspectRatio", "none")
.attr("xlink:href", ramp(color.interpolator()).toDataURL());
}
function ramp(color, n = 256) {
const canvas = document.createElement('canvas');
const context = canvas.getContext("2d");
d3.select(canvas).attr("width", n)
.attr("height", 1);
for (let i = 0; i < n; ++i) {
context.fillStyle = color(i / (n - 1));
context.fillRect(i, 0, 1, 1);
}
return canvas;
}
<script type="text/javascript" src="https://d3js.org/d3.v5.js"></script>
<div class="scatter">
</div>
By the way, there is no such element as <legend-svg>.
PS: This is the second question from you I'm answering on this subject. As you're new to JavaScript and D3, here is an advice: do not try to use that Observable notebook, that's way too complicated for your purposes. Just create the SVG, the canvas and a basic axis yourself, from scratch, it will be way easier.

avoid zoom transform from resetting after svg is clicked d3

I have a svg element ; the nodes, links, labels etc. are appended to it. I got the zoom-to-particular-node-by-name functionality running but the issue is after zooming automatically to the respective node , whenever I try to pan svg (by clicking and dragging it around), it resets the zoom and the coordinates to how it was before I zoomed to a particular node. I think it has to do with the way d3.event.transform works but I am not able to fix it. I want to be able to continue panning and zooming from the node I zoomed to without resetting any values.
(Also, from a bit of debugging , I observed that the cx and cy coordinates for the nodes did not change by zooming and panning from the code, but If I were to zoom and pan to a node manually , then it would. I guess that is the problem)
var svg1 = d3.select("svg");
var width = +screen.width;
var height = +screen.height - 500;
svg1.attr("width", width).attr("height", height);
var zoom = d3.zoom();
var svg = svg1
.call(
zoom.on("zoom", function() {
svg.attr("transform", d3.event.transform);
})
)
.on("dblclick.zoom", null)
.append("g");
function highlightNode() {
var userInput = document.getElementById("targetNode");
theNode = d3.select("#" + userInput.value);
const isEmpty = theNode.empty();
if (isEmpty) {
document.getElementById("output").innerHTML = "Given node doesn't exist";
} else {
document.getElementById("output").innerHTML = "";
}
svg
.transition()
.duration(750)
.attr(
"transform",
"translate(" +
-(theNode.attr("cx") - screen.width / 2) +
"," +
-(theNode.attr("cy") - screen.height / 4) +
")"
// This works correctly
);
}

D3 zoom v3 vs v5

I'm having trouble translating a D3 example with a zoom behavior from v3 to v5. My code is based on this example: https://bl.ocks.org/mbostock/2206340 by Mike Bostock. I use react and I get these errors "d3.zoom(...).translate is not a function" and "d3.zoom(...).scale is not a function". I looked in the documentation, but could not find scale or translate just scaleBy and translateTo and translateBy. I can't figure out how to do it either way.
componentDidMount() {
this.drawChart();
}
drawChart = () => {
var width = window.innerWidth * 0.66,
height = window.innerHeight * 0.7,
centered,
world_id;
window.addEventListener("resize", function() {
width = window.innerWidth * 0.66;
height = window.innerHeight * 0.7;
});
var tooltip = d3
.select("#container")
.append("div")
.attr("class", "tooltip hidden");
var projection = d3
.geoMercator()
.scale(100)
.translate([width / 2, height / 1.5]);
var path = d3.geoPath().projection(projection);
var zoom = d3
.zoom()
.translate(projection.translate())
.scale(projection.scale())
.scaleExtent([height * 0.197, 3 * height])
.on("zoom", zoomed);
var svg = d3
.select("#container")
.append("svg")
.attr("width", width)
.attr("class", "map card shadow")
.attr("height", height);
var g = svg.append("g").call(zoom);
g.append("rect")
.attr("class", "background")
.attr("width", width)
.attr("height", height);
var world_id = data2;
var world = data;
console.log(world);
var rawCountries = topojson.feature(world, world.objects.countries)
.features,
neighbors = topojson.neighbors(world.objects.countries.geometries);
console.log(rawCountries);
console.log(neighbors);
var countries = [];
// Splice(remove) random pieces
rawCountries.splice(145, 1);
rawCountries.splice(38, 1);
rawCountries.map(country => {
//console.log(parseInt(country.id) !== 010)
// Filter out Antartica and Kosovo
if (parseInt(country.id) !== parseInt("010")) {
countries.push(country);
} else {
console.log(country.id);
}
});
console.log(countries);
g.append("g")
.attr("id", "countries")
.selectAll(".country")
.data(countries)
.enter()
.insert("path", ".graticule")
.attr("class", "country")
.attr("d", path)
.attr("data-name", function(d) {
return d.id;
})
.on("click", clicked)
.on("mousemove", function(d, i) {
var mouse = d3.mouse(svg.node()).map(function(d) {
return parseInt(d);
});
tooltip
.classed("hidden", false)
.attr(
"style",
"left:" + mouse[0] + "px;top:" + (mouse[1] - 50) + "px"
)
.html(getCountryName(d.id));
})
.on("mouseout", function(d, i) {
tooltip.classed("hidden", true);
});
function getCountryName(id) {
var country = world_id.filter(
country => parseInt(country.iso_n3) == parseInt(id)
);
console.log(country[0].name);
console.log(id);
return country[0].name;
}
function updateCountry(d) {
console.log(world_id);
var country = world_id.filter(
country => parseInt(country.iso_n3) == parseInt(d.id)
);
console.log(country[0].name);
var iso_a2;
if (country[0].name === "Kosovo") {
iso_a2 = "xk";
} else {
iso_a2 = country[0].iso_a2.toLowerCase();
}
// Remove any current data
$("#countryName").empty();
$("#countryFlag").empty();
$("#countryName").text(country[0].name);
var src = "svg/" + iso_a2 + ".svg";
var img = "<img id='flag' class='flag' src=" + src + " />";
$("#countryFlag").append(img);
}
// Remove country when deselected
function removeCountry() {
$("#countryName").empty();
$("#countryFlag").empty();
}
// When clicked on a country
function clicked(d) {
if (d && centered !== d) {
centered = d;
updateCountry(d);
} else {
centered = null;
removeCountry();
}
g.selectAll("path").classed(
"active",
centered &&
function(d) {
return d === centered;
}
);
console.log("Clicked");
console.log(d);
console.log(d);
var centroid = path.centroid(d),
translate = projection.translate();
console.log(translate);
console.log(centroid);
projection.translate([
translate[0] - centroid[0] + width / 2,
translate[1] - centroid[1] + height / 2
]);
zoom.translate(projection.translate());
g.selectAll("path")
.transition()
.duration(700)
.attr("d", path);
}
// D3 zoomed
function zoomed() {
console.log("zoomed");
projection.translate(d3.event.translate).scale(d3.event.scale);
g.selectAll("path").attr("d", path);
}
};
render() {
return (
<div className="container-fluid bg">
<div class="row">
<div className="col-12">
<h2 className="header text-center p-3 mb-5">
Project 2 - World value survey
</h2>
</div>
</div>
<div className="row mx-auto">
<div className="col-md-8">
<div id="container" class="mx-auto" />
</div>
<div className="col-md-4">
<div id="countryInfo" className="card">
<h2 id="countryName" className="p-3 text-center" />
<div id="countryFlag" className="mx-auto" />
</div>
</div>
</div>
</div>
);
}

I won't go into the differences between v3 and v5 partly because it has been long enough that I have forgotten much of the specifics and details as to how v3 was different. Instead I'll just look at how to implement that example with v5. This answer would require adaptation for non-geographic cases - the geographic projection is doing the visual zooming in this case.
In your example, the zoom keeps track of the zoom state in order to set the projection properly. The zoom does not set a transform to any SVG element, instead the projection reprojects the features each zoom (or click).
So, to get started, with d3v5, after we call the zoom on our selection, we can set the zoom on a selected element with:
selection.call(zoom.transform, transformObject);
Where the base transform object is:
d3.zoomIdentity
d3.zoomIdentity has scale (k) of 1, translate x (x) and y (y) values of 0. There are some methods built into the identity prototype, so a plain object won't do, but we can use the identity to set new values for k, x, and y:
var transform = d3.zoomIdentity;
transform.x = projection.translate()[0]
transform.y = projection.translate()[1]
transform.k = projection.scale()
This is very similar to the example, but rather than providing the values to the zoom behavior itself, we are building an object that describes the zoom state. Now we can use selection.call(zoom.transform, transform) to apply the transform. This will:
set the zoom's transform to the provided values
trigger a zoom event
In our zoom function we want to take the updated zoom transform, apply it to the projection and then redraw our paths:
function zoomed() {
// Get the new zoom transform
transform = d3.event.transform;
// Apply the new transform to the projection
projection.translate([transform.x,transform.y]).scale(transform.k);
// Redraw the features based on the updaed projection:
g.selectAll("path").attr("d", path);
}
Note - d3.event.translate and d3.event.scale won't return anything in d3v5 - these are now the x,y,k properties of d3.event.transform
Without a click function, we might have this, which is directly adapted from the example in the question. The click function is not included, but you can still pan.
If we want to include a click to center function like the original, we can update our transform object with the new translate and call the zoom:
function clicked(d) {
var centroid = path.centroid(d),
translate = projection.translate();
// Update the translate as before:
projection.translate([
translate[0] - centroid[0] + width / 2,
translate[1] - centroid[1] + height / 2
]);
// Update the transform object:
transform.x = projection.translate()[0];
transform.y = projection.translate()[1];
// Apply the transform object:
g.call(zoom.transform, transform);
}
Similar to the v3 version - but by applying the zoom transform (just as we did initially) we trigger a zoom event, so we don't need to update the path as part of the click function.
All together that might look like this.
There is on detail I didn't include, the transition on click. As we triggering the zoomed function on both click and zoom, if we included a transition, panning would also transition - and panning triggers too many zoom events for transitions to perform as desired. One option we have is to trigger a transition only if the source event was a click. This modification might look like:
function zoomed() {
// Was the event a click?
var event = d3.event.sourceEvent ? d3.event.sourceEvent.type : null;
// Get the new zoom transform
transform = d3.event.transform;
// Apply the new transform to the projection
projection.translate([transform.x,transform.y]).scale(transform.k);
// Redraw the features based on the updaed projection:
(event == "click") ? g.selectAll("path").transition().attr("d",path) : g.selectAll("path").attr("d", path);
}

Resize svg when window is resized in d3.js

I'm drawing a scatterplot with d3.js. With the help of this question :
Get the size of the screen, current web page and browser window
I'm using this answer :
var w = window,
d = document,
e = d.documentElement,
g = d.getElementsByTagName('body')[0],
x = w.innerWidth || e.clientWidth || g.clientWidth,
y = w.innerHeight|| e.clientHeight|| g.clientHeight;
So I'm able to fit my plot to the user's window like this :
var svg = d3.select("body").append("svg")
.attr("width", x)
.attr("height", y)
.append("g");
Now I'd like that something takes care of resizing the plot when the user resize the window.
PS : I'm not using jQuery in my code.

Look for 'responsive SVG' it is pretty simple to make a SVG responsive and you don't have to worry about sizes any more.
Here is how I did it:
d3.select("div#chartId")
.append("div")
// Container class to make it responsive.
.classed("svg-container", true)
.append("svg")
// Responsive SVG needs these 2 attributes and no width and height attr.
.attr("preserveAspectRatio", "xMinYMin meet")
.attr("viewBox", "0 0 600 400")
// Class to make it responsive.
.classed("svg-content-responsive", true)
// Fill with a rectangle for visualization.
.append("rect")
.classed("rect", true)
.attr("width", 600)
.attr("height", 400);
.svg-container {
display: inline-block;
position: relative;
width: 100%;
padding-bottom: 100%; /* aspect ratio */
vertical-align: top;
overflow: hidden;
}
.svg-content-responsive {
display: inline-block;
position: absolute;
top: 10px;
left: 0;
}
svg .rect {
fill: gold;
stroke: steelblue;
stroke-width: 5px;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<div id="chartId"></div>
Note: Everything in the SVG image will scale with the window width. This includes stroke width and font sizes (even those set with CSS). If this is not desired, there are more involved alternate solutions below.
More info / tutorials:
http://thenewcode.com/744/Make-SVG-Responsive
http://soqr.fr/testsvg/embed-svg-liquid-layout-responsive-web-design.php

Use window.onresize:
function updateWindow(){
x = w.innerWidth || e.clientWidth || g.clientWidth;
y = w.innerHeight|| e.clientHeight|| g.clientHeight;
svg.attr("width", x).attr("height", y);
}
d3.select(window).on('resize.updatesvg', updateWindow);
http://jsfiddle.net/Zb85u/1/

UPDATE just use the new way from #cminatti
old answer for historic purposes
IMO it's better to use select() and on() since that way you can have multiple resize event handlers... just don't get too crazy
d3.select(window).on('resize', resize);
function resize() {
// update width
width = parseInt(d3.select('#chart').style('width'), 10);
width = width - margin.left - margin.right;
// resize the chart
x.range([0, width]);
d3.select(chart.node().parentNode)
.style('height', (y.rangeExtent()[1] + margin.top + margin.bottom) + 'px')
.style('width', (width + margin.left + margin.right) + 'px');
chart.selectAll('rect.background')
.attr('width', width);
chart.selectAll('rect.percent')
.attr('width', function(d) { return x(d.percent); });
// update median ticks
var median = d3.median(chart.selectAll('.bar').data(),
function(d) { return d.percent; });
chart.selectAll('line.median')
.attr('x1', x(median))
.attr('x2', x(median));
// update axes
chart.select('.x.axis.top').call(xAxis.orient('top'));
chart.select('.x.axis.bottom').call(xAxis.orient('bottom'));
}
http://eyeseast.github.io/visible-data/2013/08/28/responsive-charts-with-d3/

It's kind of ugly if the resizing code is almost as long as the code for building the graph in first place. So instead of resizing every element of the existing chart, why not simply reloading it? Here is how it worked for me:
function data_display(data){
e = document.getElementById('data-div');
var w = e.clientWidth;
// remove old svg if any -- otherwise resizing adds a second one
d3.select('svg').remove();
// create canvas
var svg = d3.select('#data-div').append('svg')
.attr('height', 100)
.attr('width', w);
// now add lots of beautiful elements to your graph
// ...
}
data_display(my_data); // call on page load
window.addEventListener('resize', function(event){
data_display(my_data); // just call it again...
}
The crucial line is d3.select('svg').remove();. Otherwise each resizing will add another SVG element below the previous one.

In force layouts simply setting the 'height' and 'width' attributes will not work to re-center/move the plot into the svg container. However, there's a very simple answer that works for Force Layouts found here. In summary:
Use same (any) eventing you like.
window.on('resize', resize);
Then assuming you have svg & force variables:
var svg = /* D3 Code */;
var force = /* D3 Code */;
function resize(e){
// get width/height with container selector (body also works)
// or use other method of calculating desired values
var width = $('#myselector').width();
var height = $('#myselector').height();
// set attrs and 'resume' force
svg.attr('width', width);
svg.attr('height', height);
force.size([width, height]).resume();
}
In this way, you don't re-render the graph entirely, we set the attributes and d3 re-calculates things as necessary. This at least works when you use a point of gravity. I'm not sure if that's a prerequisite for this solution. Can anyone confirm or deny ?
Cheers, g

If you want to bind custom logic to resize event, nowadays you may start using ResizeObserver browser API for the bounding box of an SVGElement.
This will also handle the case when container is resized because of the nearby elements size change.
There is a polyfill for broader browser support.
This is how it may work in UI component:
function redrawGraph(container, { width, height }) {
d3
.select(container)
.select('svg')
.attr('height', height)
.attr('width', width)
.select('rect')
.attr('height', height)
.attr('width', width);
}
// Setup observer in constructor
const resizeObserver = new ResizeObserver((entries, observer) => {
for (const entry of entries) {
// on resize logic specific to this component
redrawGraph(entry.target, entry.contentRect);
}
})
// Observe the container
const container = document.querySelector('.graph-container');
resizeObserver.observe(container)
.graph-container {
height: 75vh;
width: 75vw;
}
.graph-container svg rect {
fill: gold;
stroke: steelblue;
stroke-width: 3px;
}
<script src="https://unpkg.com/resize-observer-polyfill#1.5.1/dist/ResizeObserver.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<figure class="graph-container">
<svg width="100" height="100">
<rect x="0" y="0" width="100" height="100" />
</svg>
</figure>
// unobserve in component destroy method
this.resizeObserver.disconnect()

For those using force directed graphs in D3 v4/v5, the size method doesn't exist any more. Something like the following worked for me (based on this github issue):
simulation
.force("center", d3.forceCenter(width / 2, height / 2))
.force("x", d3.forceX(width / 2))
.force("y", d3.forceY(height / 2))
.alpha(0.1).restart();

Dynamic viewport for d3.js [duplicate]

Assume I have a histogram script that builds a 960 500 svg graphic. How do I make this responsive so on resize the graphic widths and heights are dynamic?
<script>
var n = 10000, // number of trials
m = 10, // number of random variables
data = [];
// Generate an Irwin-Hall distribution.
for (var i = 0; i < n; i++) {
for (var s = 0, j = 0; j < m; j++) {
s += Math.random();
}
data.push(s);
}
var histogram = d3.layout.histogram()
(data);
var width = 960,
height = 500;
var x = d3.scale.ordinal()
.domain(histogram.map(function(d) { return d.x; }))
.rangeRoundBands([0, width]);
var y = d3.scale.linear()
.domain([0, d3.max(histogram.map(function(d) { return d.y; }))])
.range([0, height]);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
svg.selectAll("rect")
.data(histogram)
.enter().append("rect")
.attr("width", x.rangeBand())
.attr("x", function(d) { return x(d.x); })
.attr("y", function(d) { return height - y(d.y); })
.attr("height", function(d) { return y(d.y); });
svg.append("line")
.attr("x1", 0)
.attr("x2", width)
.attr("y1", height)
.attr("y2", height);
</script>
Full example histogram gist is:
https://gist.github.com/993912

There's another way to do this that doesn't require redrawing the graph, and it involves modifying the viewBox and preserveAspectRatio attributes on the <svg> element:
<svg id="chart" viewBox="0 0 960 500"
preserveAspectRatio="xMidYMid meet">
</svg>
Update 11/24/15: most modern browsers can infer the aspect ratio of SVG elements from the viewBox, so you may not need to keep the chart's size up to date. If you need to support older browsers, you can resize your element when the window resizes like so:
var aspect = width / height,
chart = d3.select('#chart');
d3.select(window)
.on("resize", function() {
var targetWidth = chart.node().getBoundingClientRect().width;
chart.attr("width", targetWidth);
chart.attr("height", targetWidth / aspect);
});
And the svg contents will be scaled automatically. You can see a working example of this (with some modifications) here: just resize the window or the bottom right pane to see how it reacts.

Look for 'responsive SVG' it is pretty simple to make a SVG responsive and you don't have to worry about sizes any more.
Here is how I did it:
d3.select("div#chartId")
.append("div")
.classed("svg-container", true) //container class to make it responsive
.append("svg")
//responsive SVG needs these 2 attributes and no width and height attr
.attr("preserveAspectRatio", "xMinYMin meet")
.attr("viewBox", "0 0 600 400")
//class to make it responsive
.classed("svg-content-responsive", true);
The CSS code:
.svg-container {
display: inline-block;
position: relative;
width: 100%;
padding-bottom: 100%; /* aspect ratio */
vertical-align: top;
overflow: hidden;
}
.svg-content-responsive {
display: inline-block;
position: absolute;
top: 10px;
left: 0;
}
More info / tutorials:
http://demosthenes.info/blog/744/Make-SVG-Responsive
http://soqr.fr/testsvg/embed-svg-liquid-layout-responsive-web-design.php

I've coded up a small gist to solve this.
The general solution pattern is this:
Breakout the script into computation and drawing functions.
Ensure the drawing function draws dynamically and is driven of
visualisation width and height variables (The best way to do this is
to use the d3.scale api)
Bind/chain the drawing to a reference
element in the markup. (I used jquery for this, so imported it).
Remember to remove it if it's already drawn. Get the dimensions from
the referenced element using jquery.
Bind/chain the draw function to
the window resize function. Introduce a debounce (timeout) to this
chain to ensure we only redraw after a timeout.
I also added the minified d3.js script for speed.
The gist is here: https://gist.github.com/2414111
jquery reference back code:
$(reference).empty()
var width = $(reference).width();
Debounce code:
var debounce = function(fn, timeout)
{
var timeoutID = -1;
return function() {
if (timeoutID > -1) {
window.clearTimeout(timeoutID);
}
timeoutID = window.setTimeout(fn, timeout);
}
};
var debounced_draw = debounce(function() {
draw_histogram(div_name, pos_data, neg_data);
}, 125);
$(window).resize(debounced_draw);
Enjoy!

Without Using ViewBox
Here is an example of a solution that does not rely on using a viewBox:
The key is in updating the range of the scales which are used to place data.
First, calculate your original aspect ratio:
var ratio = width / height;
Then, on each resize, update the range of x and y:
function resize() {
x.rangeRoundBands([0, window.innerWidth]);
y.range([0, window.innerWidth / ratio]);
svg.attr("height", window.innerHeight);
}
Note that the height is based on the width and the aspect ratio, so that your original proportions are maintained.
Finally, "redraw" the chart – update any attribute that depends on either of the x or y scales:
function redraw() {
rects.attr("width", x.rangeBand())
.attr("x", function(d) { return x(d.x); })
.attr("y", function(d) { return y.range()[1] - y(d.y); })
.attr("height", function(d) { return y(d.y); });
}
Note that in re-sizing the rects you can use the upper-bound of the range of y, rather than explicitly using the height:
.attr("y", function(d) { return y.range()[1] - y(d.y); })
var n = 10000, // number of trials
m = 10, // number of random variables
data = [];
// Generate an Irwin-Hall distribution.
for (var i = 0; i < n; i++) {
for (var s = 0, j = 0; j < m; j++) {
s += Math.random();
}
data.push(s);
}
var histogram = d3.layout.histogram()
(data);
var width = 960,
height = 500;
var ratio = width / height;
var x = d3.scale.ordinal()
.domain(histogram.map(function(d) {
return d.x;
}))
var y = d3.scale.linear()
.domain([0, d3.max(histogram, function(d) {
return d.y;
})])
var svg = d3.select("body").append("svg")
.attr("width", "100%")
.attr("height", height);
var rects = svg.selectAll("rect").data(histogram);
rects.enter().append("rect");
function redraw() {
rects.attr("width", x.rangeBand())
.attr("x", function(d) {
return x(d.x);
})
// .attr("y", function(d) { return height - y(d.y); })
.attr("y", function(d) {
return y.range()[1] - y(d.y);
})
.attr("height", function(d) {
return y(d.y);
});
}
function resize() {
x.rangeRoundBands([0, window.innerWidth]);
y.range([0, window.innerWidth / ratio]);
svg.attr("height", window.innerHeight);
}
d3.select(window).on('resize', function() {
resize();
redraw();
})
resize();
redraw();
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>

Lots of complex answers here.
Basically all you need to do is ditch the width and height attributes in favor of the viewBox attribute:
width = 500;
height = 500;
const svg = d3
.select("#chart")
.append("svg")
.attr("viewBox", `0 0 ${width} ${height}`)
If you have margins, you can just add them there into the width/height then just append the g thereafter and transform it like you would normally.

If you are using d3.js through c3.js the solution to the responsiveness issue is quite straightforward :
var chart = c3.generate({bindTo:"#chart",...});
chart.resize($("#chart").width(),$("#chart").height());
where the generated HTML looks like :
<div id="chart">
<svg>...</svg>
</div>

In the case that you are using a d3 wrapper like plottable.js, be aware that the easiest solution might be adding an event listener and then calling a redraw function (redraw in plottable.js). In the case of plottable.js this will work excellently (this approach is poorly documented):
window.addEventListener("resize", function() {
table.redraw();
});

Shawn Allen's answer was great. But you may not want to do this every single time. If you host it on vida.io, you get automatic responsive for your svg visualization.
You can get responsive iframe with this simple embed code:
<div id="vida-embed">
<iframe src="http://embed.vida.io/documents/9Pst6wmB83BgRZXgx" width="auto" height="525" seamless frameBorder="0" scrolling="no"></iframe>
</div>
#vida-embed iframe {
position: absolute;
top:0;
left: 0;
width: 100%;
height: 100%;
}
http://jsfiddle.net/dnprock/npxp3v9d/1/
Disclosure: I build this feature at vida.io.

In case people are still visiting this question - here’s what worked for me:
Enclose the iframe in a div and use css to add a padding of, say, 40% to that div (the percentage depending on the aspect ratio you want). Then set both width and height of the iframe itself to 100%.
In the html doc containing the chart to be loaded in the iframe, set width to the width of the div that the svg is appended to (or to the width of the body) and set height to width * aspect ratio.
Write a function that reloads the iframe content upon window resize, so as to adapt the size of the chart when people rotate their phone.
Example here on my website:
http://dirkmjk.nl/en/2016/05/embedding-d3js-charts-responsive-website
UPDATE 30 Dec 2016
The approach I described above has some drawbacks, especially that it doesn’t take the height into account of any title and captions that are not part of the D3-created svg. I’ve since come across what I think is a better approach:
Set the width of the D3 chart to the width of the div it’s attached to and use the aspect ratio to set its height accordingly;
Have the embedded page send its height and url to the parent page using HTML5’s postMessage;
On the parent page, use the url to identify the corresponding iframe (useful if you have more than one iframe on your page) and update its height to the height of the embedded page.
Example here on my website: http://dirkmjk.nl/en/2016/12/embedding-d3js-charts-responsive-website-better-solution

One of the basic principles of the D3 data-join is that it is idempotent. In other words, if you repeatedly evaluate a data-join with the same data, the rendered output is the same. Therefore, as long as you render your chart correctly, taking care withe your enter, update and exit selections - all you have to do when the size changes, is re-render the chart in its entirety.
There are a couple of other things you should do, one is de-bounce the window resize handler in order to throttle it. Also, rather than hard-coding widths / heights, this should be achieved by measuring the containing element.
As an alternative, here is your chart rendered using d3fc, which is a set of D3 components that correctly handle data-joins. It also has a cartesian chart that measures it containing element making it easy to create 'responsive' charts:
// create some test data
var data = d3.range(50).map(function(d) {
return {
x: d / 4,
y: Math.sin(d / 4),
z: Math.cos(d / 4) * 0.7
};
});
var yExtent = fc.extentLinear()
.accessors([
function(d) { return d.y; },
function(d) { return d.z; }
])
.pad([0.4, 0.4])
.padUnit('domain');
var xExtent = fc.extentLinear()
.accessors([function(d) { return d.x; }]);
// create a chart
var chart = fc.chartSvgCartesian(
d3.scaleLinear(),
d3.scaleLinear())
.yDomain(yExtent(data))
.yLabel('Sine / Cosine')
.yOrient('left')
.xDomain(xExtent(data))
.xLabel('Value')
.chartLabel('Sine/Cosine Line/Area Chart');
// create a pair of series and some gridlines
var sinLine = fc.seriesSvgLine()
.crossValue(function(d) { return d.x; })
.mainValue(function(d) { return d.y; })
.decorate(function(selection) {
selection.enter()
.style('stroke', 'purple');
});
var cosLine = fc.seriesSvgArea()
.crossValue(function(d) { return d.x; })
.mainValue(function(d) { return d.z; })
.decorate(function(selection) {
selection.enter()
.style('fill', 'lightgreen')
.style('fill-opacity', 0.5);
});
var gridlines = fc.annotationSvgGridline();
// combine using a multi-series
var multi = fc.seriesSvgMulti()
.series([gridlines, sinLine, cosLine]);
chart.plotArea(multi);
// render
d3.select('#simple-chart')
.datum(data)
.call(chart);
You can see it in action in this codepen:
https://codepen.io/ColinEberhardt/pen/dOBvOy
where you can resize the window and verify that the chart is correctly re-rendered.
Please note, as a full disclosure, I am one of the maintainers of d3fc.

I would avoid resize/tick solutions like the plague since they are inefficient and can cause issues in your app (e.g. a tooltip re-calculates the position it should appear on window resize, then a moment later your chart resizes too and the page re-layouts and now your tooltip is wrong again).
You can simulate this behaviour in some older browsers that don't properly support it like IE11 too using a <canvas> element which maintains it's aspect.
Given 960x540 which is an aspect of 16:9:
<div style="position: relative">
<canvas width="16" height="9" style="width: 100%"></canvas>
<svg viewBox="0 0 960 540" preserveAspectRatio="xMidYMid meet" style="position: absolute; top: 0; right: 0; bottom: 0; left: 0; -webkit-tap-highlight-color: transparent;">
</svg>
</div>

You can also use bootstrap 3 to adapt the size of a visualization. For example, we can set up the HTML code as:
<div class="container>
<div class="row">
<div class='col-sm-6 col-md-4' id="month-view" style="height:345px;">
<div id ="responsivetext">Something to write</div>
</div>
</div>
</div>
I have set up a fixed height because of my needs, but you can leave the size auto as well. The "col-sm-6 col-md-4" makes the div responsive for different devices. You can learn more at http://getbootstrap.com/css/#grid-example-basic
We can access the graph with the help of the id month-view.
I won't go into much detail about the d3 code, I will only input the part that is needed for adapting to different screen sizes.
var width = document.getElementById('month-view').offsetWidth;
var height = document.getElementById('month-view').offsetHeight - document.getElementById('responsivetext2').offsetHeight;
The width is set by getting the width of the div with the id month-view.
The height in my case should not include the entire area. I also have some text above the bar so I need to calculate that area as well. That's why I identified the area of the text with the id responsivetext. For calculating the allowed height of the bar, I subtracted the height of the text from the height of the div.
This allows you to have a bar that will adopt all the different screen/div sizes. It might not be the best way of doing it, but it surely works for the needs of my project.